In optical communications, many modulation schemes have been used to transport data. On-Off keying (OOK) is one modulation scheme that has been used, where data is encoded using signal intensity variation. OOK introduces strong characteristic tones in the signal frequency domain, which can be detected as periodic intensity variations in the signal. To detect the signals, a conventional clock recovery scheme is used to obtain the timing information in the tones, such as by filtering the detected signal intensities using a narrow band pass filter. Phase Shift Keying (PSF) is another modulation scheme that has been used more recently. In PSF, the data is encoded using signal phase variation. Therefore, the conventional clock recovery for OOK, which is based on detecting signal intensities, is not suitable for PSF modulation. Instead, other clock recovery algorithms have been proposed for PSF, such as early-late gate, Mueller-Muller, and Gardner algorithms. These algorithms are based on the assumption that the distortion of the signal passing through an optical fiber, e.g. due to fiber dispersion and polarization mode dispersion (PMD), is relatively small with respect to the signal and thus the rising/falling edge of the signal can be easily detected. However, for higher data transmission rates, such as 100 Gigabit systems, the signal can be highly distorted due to fiber dispersion and PMD and the rising/falling edge of the signal cannot be easily detected. Therefore, other clock recovery algorithms that are based on timing information in the signal are used.